The invention lies in the field of vehicle occupant protection systems. The invention relates to a vehicle occupant protection system for a motor vehicle having at least one accident sensor and one control device that controls the triggering of the vehicle occupant protection system as a function of the sensor output signal. The accident sensor registers a parameter that characterizes an accident, in particular, an acceleration of a motor vehicle, an angle of inclination of a motor vehicle, and/or a rolling movement. If predefined limiting values are reached, the control device actuates the triggering of the vehicle occupant protection system. The vehicle occupant protection system may be embodied as an airbag system, a seat belt pretensioning system, a rollover bar triggering system, or in some other way.
However, if the output signal generated by the accident sensor was incorrect, there is a risk that an unnecessary and very undesirable triggering of the vehicle occupant protection system occurs, or that a necessary triggering does not occur.
German Published, Non-Prosecuted Patent Application DE 43 44 284 A1 discloses a semiconductor acceleration measuring device that is suitable, for example, for use in vehicles. The device has an acceleration sensor and a diagnostic circuit that checks whether or not the output signal generated by the acceleration sensor and amplified by an amplifier circuit is abnormal. The device is mounted on the measuring projection of the sensor.
German Published, Non-Prosecuted Patent Application DE 37 06 765 A1 discloses a motor vehicle impact sensor that is connected to a test circuit and that has an acceleration sensor. For a function test, an electro-acoustic transducer disposed in the sensor housing subjects the acceleration sensor to sound waves. The electrical signals that are generated by the acceleration sensor in reaction thereto are checked in an evaluation and triggering circuit. The check can be carried out before a journey starts, and also at regular time intervals during the journey.
German Published, Non-Prosecuted Patent Application DE 44 24 020 A1, corresponding to U.S. Pat. No. 5,726,887 describes a test method for a vehicle occupant protection system in which test pulses that are registered by downstream signal-conditioning and control components and are evaluated to check functions, are applied to the output line of the collision sensor.
German Published, Non-Prosecuted Patent Application DE 43 16 263 A1 discloses a method for diagnosing the operational capability of an acceleration sensor in which a diagnostic voltage is applied to a fixed electrode of the acceleration sensor. The resulting deflection of a movable electrode is registered and evaluated.
It is accordingly an object of the invention to provide a vehicle occupant protection system for a motor vehicle and method for controlling the triggering of the vehicle occupant protection system that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that reduces the risk of triggering errors in the vehicle occupant protection system controller.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a vehicle occupant protection system for a motor vehicle, including an accident sensor for registering an operating parameter that signals an accident, the accident sensor having an internal error-checking function, a sensor output signal terminal for carrying a sensor output signal, and a status signal output terminal for outputting a status signal, and a control device for controlling a triggering of a vehicle occupant protection system as a function of the sensor output signal, the control device connected to the accident sensor through the sensor output signal terminal, the control device having an input terminal connected to the status signal output terminal of the accident sensor through a line, the internal error-checking function of the accident sensor permanently outputting a status signal to the control device when an internal error is registered.
In accordance with an added feature of the invention, the accidence sensor is an acceleration sensor.
In accordance with an additional feature of the invention, the accident sensor registers an operating parameter that signals a motor vehicle acceleration.
The accident sensor is equipped with an error-checking function for detecting internal errors and, when an error is detected, it permanently outputs a status signal to the superordinate control device. The control device can, thus, detect, at any time, whether or not the sensor output signal that is generated by the accident sensor and that represents the monitored parameter (for example, the acceleration), is incorrect. Then, the control device can initiate suitable protective measures, for example, generate an audible and/or visible warning for the driver and can further refrain from evaluating the sensor output signal. The accident sensor is provided with an additional status signal output terminal that is specially reserved for outputting the status signal. The output terminal is connected to a terminal of the control device through a separate line. Thus, the status signal can be transmitted to the control device on a separate line and, therefore, be interrogated independently of, and in addition to, the actual sensor output signal. The interrogation frequency is preferably lower than the interrogation clock rate of the sensor output signal so that the additional loading of the control device that is caused by the status signal interrogation remains low. The accident sensor can also have a test terminal through which the control device can actively supply, in a start phase, a test signal for a function test.
In accordance with another feature of the invention, the control device has an input/output terminal through which the control device outputs a test signal to the accident sensor during a test phase.
In accordance with a further feature of the invention, the control device periodically interrogates the status signal.
The accident sensor also permanently stores a status signal that occurs only briefly. The information may be helpful during subsequent maintenance and/or diagnosis of the accident sensor and/or may also bring forward maintenance/diagnosis of the accident sensor.
The error-checking function can, for example, be an error-detection check performed on sensor operating control data that is read out of a sensor memory. The sensor operating control data can, for example, be provided with a parity bit. As such, the sensor carries out a parity check while the sensor operating control data is read out, and generates the status signal if the parity check happens to generate a data error. The error-checking function can, however, also be configured to check internal mechanical and/or electrical defects in the sensor.
A still further improved degree of protection against undesired triggering caused by sensor errors can be obtained by interrogating the sensor status signal once more just before actual triggering of the vehicle occupant protection system (due to a sensor output signal that signals an accident). The vehicle occupant protection system is triggered only if the condition of the status signal indicates that the accident sensor is operating free of errors, otherwise it is disabled.
With the objects of the invention in view, there is also provided a method for controlling the triggering of a vehicle occupant protection system, that includes performing an internal error check at regular and/or irregular intervals with an accident sensor, outputting, with the accident sensor, a status signal to a control device through a status signal output terminal when an error is detected, checking, with the control device, a status of the status signal before triggering a vehicle occupant protection system when the control device receives from the accident sensor a sensor output signal that fulfills triggering criteria for triggering a vehicle occupant protection system, and the control device enabling or disabling the triggering as a function of the result of the check. The method can be applied with the vehicle occupant protection system according to the invention.
In accordance with a concomitant mode of the invention, the control device at least one of disables future triggering of the vehicle occupant protection system when the status signal is received and generates at least one of a visual and audible warning when the status signal is received.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a vehicle occupant protection system for a motor vehicle and method for controlling the triggering of the vehicle occupant protection system, it is, nevertheless, not intended to be limited to the details shown since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.